The Study Of Properties Improvement Of Cathode Material Li₂FeSiO₄/C For Lithium-ion Battery

Lithium-ion battery is currently one of the most widely used andstudied cells, The researches of it are mainly focused on its positiveelectrode material. Li₂FeSiO₄, due to its advantages of cheap price,non-toxicity and environment-friendly, receives wide attention, but itslow electronic and ionic conductivity restrict its development. Thispaper aims at improving the electrochemical performance ofLi₂FeSiO₄in the way of doping, coating, and other different preparati-on methods.In the research of ion doping, we use Ce as doping agent andadopt solid-state method to get Li_2-3xCexFeSiO₄/C cathode material.Through the test of electrochemical performance, we find thatLi_2-3xCexFeSiO₄/C sample has the best electrochemical performancewhen the content of Ce doped is0.5%. At a C/16rate, the firstdischarge specific capacity of Li1.985Ce0.005FeSiO₄/C is117.01mAh·g^-1and the discharge capacity is101.1mAh·g^-1after20cycles. Thecapacity retention ratio remains86.4%; Li1.985Ce0.005FeSiO₄/C cathodematerial was also prepared by solid-state and sol-gel methodsseparately. By comparision, we find the first discharge capacity ofLi1.985Ce0.005FeSiO₄/C prepared by sol-gel method is117.93mAh·g^-1,and the discharge capacity is103.58mAh·g^-1after20cycles. The ca-pacity retention ratio is87.8%, showing the best electrochemical performance and the kinetic behaviors than that of solid method.In the synthetic materials modification research, we use traceFe power as a part of Fe source and adopt solid-state method to getLi₂FeSiO₄/C cathode material. Through the test of electrochemicalperformance, we find that Li₂FeSiO₄/C sample has the best electroc-hemical performance when the content of iron power is for0.5%ofiron source. At a C/16rate, the first discharge capacity of Li₂FeSiO₄/C is113.1mAh·g^-1and the discharge capacity is96.1mAh·g^-1after20cycles.The capacity retention ratio remains85%. When the contentof iron power is0.5%of iron source, Li₂FeSiO₄/C cathode material isprepared by tradition solid-state and improved solid-state methodsseparately. The results indicate that Li₂FeSiO₄/C prepared byimproved solid-state method have good charge-discharge capacityand excellent electrochemical performance.Sol-gel method is employed to prepare Li₂Fe_1/3Co_1/3Zn_1/3SiO₄/CandLi₂FeSiO₄/C. In order to get the optimum synthetic condition, pH,solution concentration, temperature and many important parameterswere analyzed in this technology. It is concluded from the x-raydiffraction spectrum diagram analysis that the Li₂Fe_1/3Co_1/3Zn_1/3SiO₄/Cdiff-raction peak is in good agreement with the structure of Li₂CoSiO₄, w-hose electrochemical performance is better. To avoid long dryingcycle for wet gel, microwave drying was used instead of vacuumdrying, and it has many advantages including short synthetic time,environment friendly and the like.